“A little boy should not have to say goodbye to his partner in crime, his playmate, his best friend, his little sister,” Sooter wrote. “This isn’t how it’s supposed to be. But this is the broken world we live in.”

Sooter said that Addy’s symptoms “progressed rapidly” before she died.

A celebration of life for Addy was held in Arkansas over the weekend with people from around the world watching live on Facebook.